1. Field of the Invention
The present invention relates to an electronic musical instrument which simulates a tone-generation mechanism of a non-electronic musical instrument so as to synthesize its sounds.
2. Prior Art
Conventionally, a physical sound source as disclosed in Japanese Patent Laid-Open Publication No. 63-40199 is well known as the sound source which simulates the tone-generation mechanism of the non-electronic musical instrument. This physical sound source contains the non-linear circuit and transmission circuit. The non-linear circuit is designed to simulate the generation of the vibration applied to the sounding element of the non-electronic musical instrument, while the transmission circuit is designed to simulate the propagation of the sound to be transmitted onto the string or through the tube portion.
The above-mentioned non-linear circuit outputs a predetermined excitation signal in accordance with several kinds of parameters relating to the musical tone to be generated. The excitation signal is supplied to the transmission circuit. The transmission circuit is configured as a loop circuit containing a delay circuit, a low-pass filter and the like, so that the excitation signal is circulated through the loop circuit. Such excitation signal to be circulated through the loop circuit is fed back to the non-linear circuit as its input signal. As described above, the signal circulating through the non-linear circuit and transmission circuit is picked up at an arbitrary point of the loop circuit as a musical tone signal. A musical tone is generated by a predetermined musical tone generation device in response to the musical tone signal.
The above-mentioned, so-called delay-feedback-type sound source mainly operates to perform the simulation of the non-electronic musical instrument. Herein, its delay length is determined by the musical interval or length of the string or tube of the instrument to be simulated.
However, the conventional electronic musical instrument providing the above-mentioned sound source cannot simulate all of the operations of a non-electronic musical instrument with accuracy. Therefore, some of the simulated operations may be slightly different from the actual operations of the non-electronic musical instrument. For example, in the non-electronic musical instrument, it can be observed that a small pitch variation (or pitch-rising phenomenon) is occurred at the start time of the tone-generation.
In the conventional electronic musical instrument, the pitch of the musical tone to be generated must be determined to completely match with the delay length to be set at once. Therefore, it cannot perform an active control on the musical tone in its tone-generation process. Thus, it is very difficult to simulate the above-mentioned pitch-rising phenomenon with accuracy.